bimini frame type

I have been searching for new fabric for my bimini top. In my internet searches I have found that some dealers need to know the “frame type”, either O or Q or other letters. All I know is that it is a 4 bow frame. I figured that tops to fit a 4 bow frame were all the same. Am I wrong?

Can anyone tell me how to figure out what frame type I have? I don’t want to buy the wrong one.

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